Haematological studies were conducted in recently weaned guinea pigs fed selenium-enriched barley (organic selenium) and barley mixed with sodium selenite (inorganic selenium). An attempt was made to study the effect of sodium arsenite supplementation in sodium selenite toxicity. A significant (p < 0.01) decrease was noticed in the mean values of haemoglobin, haematocrit, mean corpuscular haemoglobin and mean corpuscular volume thereby indicating a microcytic hypochromic anaemia. The anaemia was comparatively more marked in guinea pigs fed selenium-enriched barley than in those kept on barley mixed with sodium selenite. There was a significant decrease in total leucocyte count which was the result of lymphocytopenia in organic toxicity and a decrease in both neutrophils and lymphocytes in inorganic toxicity. Dietary supplementation with sodium arsenite resulted in less reduction in the mean values of different erythrocytic indices thereby indicating that addition of sodium arsenite has some protective effect against toxicity with sodium selenite.